`text{Đáp án:}`
`a)x=-22`
`b)x=35`
`c)x=84`
`text{Giải thích các bước giải:}`
`a)3-(17-x)=289-(36+289)`
`⇔3-(17-x)=-36`
`⇔17-x=3-(-36)`
`⇔17-x=39`
`⇔x=17-39`
`⇔x=-22`
`b)25-(x+5)=-415-(15-415)`
`⇔25-(x+5)=-15`
`⇔x+5=25-(-15)`
`⇔x+5=40`
`⇔x=40-5`
`⇔x=35`
`c)34+(21-x)=(3747-30)-3746`
`⇔34+(21-x)=3747-3746-30`
`⇔34+(21-x)=-29`
`⇔21-x=-29-34`
`⇔21-x=-63`
`⇔x=21-(-63)`
`⇔x=84`